PL212423B1 - Security paper and method for the production thereof - Google Patents

Abstract

Security paper, for the production of documents of value such as bank notes, passports and identity papers, comprises a flat substrate at least partially covered with a dirt-repellent protective layer comprising at least two lacquer layers to protect the substrate from physical and chemical effects. Security paper (I), for the production of documents of value such as bank notes, passports and identity papers, comprises a flat substrate (A) at least partially covered with a dirt-repellent protective layer (B) to increase its life whereby the protective layer (B) comprises at least two lacquer layers (B1 and B2) such that the lower layer (B1) is applied to the substrate (A) as a physically drying lacquer layer that is in contact with the substrate (A) and closes its pores and the upper layer (B2) protects the substrate (A) from physical and chemical effects. Independent claims are included for: (1) documents of value produced from the paper (I) and; (2) a process for the production of the paper (I) by preparation of a flat substrate (A), application of a lacquer layer (B1) and layer (B2).

Description

The present invention relates to a security paper for the production of security documents such as bank notes, passports, identification documents and the like, as well as the use of said security paper for the production of a security document and a method of producing such security paper.

Valuable and security documents such as banknotes, stocks, bonds, certificates and coupons, checks, high-quality admission tickets, as well as other documents prone to forgery, such as passports, often have carefully printed images, which is to increase the security of documents against forgery. High-tech printing processes, such as gravure printing, which are not available to everyone, are used to print at least some of the elements of these images.

The security prints are additionally often provided with so-called security elements which are difficult to counterfeit and make it possible to verify the authenticity of the print or document even by a layman in the field. Such security elements can be, for example, windowed security threads which are visible in certain areas on the surface of the value document, superimposed films having a transparent or metallized hologram embossed, invisible embossing, so-called "hidden images" made by printing techniques or by a combination of printing techniques with embossing, so that at different viewing angles you can see different information, prints made with optically variable pigments and, depending on the viewing angle, with different color effects, or prints with metallic inks that have a metallic effect shine in a shade of, for example, gold, silver or bronze.

An important element of value documents such as banknotes is their flat substrate, which preferably consists mainly of cotton paper, the tactile impression provided by the paper being influenced by one-sided or two-sided calendering during the steel engraving process. The tactile sensation of a banknote is mainly due to its tactile properties and its stiffness when bent; a distinctive sound is also heard when it wrinkles or deforms.

It is known in the art to provide valuable documents with a dirt-repellent layer, thereby increasing the durability and suitability of the document for circulation. For example, EP 0 256 170 B2 proposes to provide printed banknotes with a protective layer which consists mainly of cellulose ester or cellulose ether and to a lesser extent of micronized wax, this layer covering the entire surface of the notes. Micronized wax is dispersed by kneading or mixing with oil, ink binder, or a mixture thereof. Sheets having a freshly printed protective layer can be stacked without fear without the risk of being stained by black ink from the underlying sheet.

WO 00/00697 discloses a security paper for the production of banknotes which has a soil-repellent coating, the characteristics of which, such as printability, sound, color, remain largely unchanged compared to uncoated paper. Consisting only of an unfilled binder, the coating composition is applied to the banknote paper, the paper having a large surface area or a high surface roughness because of its porosity. The composition is applied as a layer with a thickness selected such that a smooth surface is obtained with little potential for dirt to settle, but the coating is so thin that it does not affect other properties of the paper.

A common feature of the prior art protective layers is that the degree of protection against paper wear is not particularly high. Conventional water-dilutable varnish protective layers usually do not fully comply with the desired set of properties. For example, very high dirt resistance and adhesion do not go hand in hand with resistance to liquid penetration and vice versa. Water-dilutable varnishes therefore meet the high requirements of the presently high requirements for their use as a protective layer in security prints, and in particular banknote prints, only when a second crosslinker component is added thereto. Because such cross-linking agents

Since they are very chemically active, the personnel must be sensitized to the hazards, and appropriate protective measures must be taken.

The invention therefore relates to the problem of providing a security paper and a method for its production, which do not suffer from the difficulties of the prior art. The security paper should, in particular, have a longer shelf life due to its high resistance to dirt and liquid penetration.

This problem is solved by providing the security paper according to the invention.

The present invention relates to a security paper for the production of valuable documents such as bank notes, passports, identification documents and the like, comprising a flat backing which at least partially has a protective layer against dirt, extending the durability and suitability of the document for use in circulation. that the protective layer comprises at least two varnish layers, the first lower varnish layer being formed as a layer of physically drying varnish applied to the substrate, in contact with the underlying substrate and closing its pores, where this layer is based on the diluted substrate. with water a dispersion of aliphatic polyester polyurethanes or styrene-acrylic polyurethanes, and the second upper layer of varnish is a layer protecting the substrate against the influence of physical and chemical factors and is made of one of the following layers:

a) UV-crosslinkable lacquer layer;

b) a layer of physically drying varnish based on an aqueous dispersion based on styrene-acrylic without a polyurethane component;

c) a hybrid varnish layer containing both physically drying components and a radiation curable varnish component, based on an aqueous dispersion based on aliphatic urethane acrylates and acrylates with photoinitiators.

Preferably, the substrate is in the form of unprinted or printed cotton paper.

Preferably, the lower lacquer layer forms a smooth and contiguous layer on the substrate.

Preferably, the first bottom lacquer layer is flexible.

Preferably, the second, top lacquer layer comprises silicones and / or wax.

Preferably, the UV-crosslinkable lacquer layer is based on an acrylate system.

Preferably, the composition of the upper lacquer layer is selected with regard to its brittleness and surface tension.

Preferably, the top lacquer layer is located directly on the bottom lacquer layer.

Preferably, between the upper lacquer layer and the lower lacquer layer, a further lacquer layer made with the use of a water-dilutable dispersion lacquer is placed.

Preferably, the lacquer layers constituting the protective layer have matching adhesive characteristics.

Preferably, the lower lacquer layer has a low glass transition temperature.

Preferably, the top lacquer layer and / or the bottom lacquer layer are transparent and colorless.

Advantageously, the top lacquer layer is protected against the action of bacteria and fungi.

Preferably, the lower lacquer layer is arranged on a substrate in a coating weight of from 1 to 6 g / m ^2, preferably from 2 to 4 g / m ^2.

Preferably, the upper lacquer layer is arranged on the substrate as a coating having a weight of from 0.5 to 3 g / m ^2, more preferably 1 to 2 g / m ^2.

Preferably, the substrate is printed with letters or patterns, and the protective layer is applied to the printed substrate and / or a lower lacquer layer is printed onto which is applied an upper lacquer layer and / or a second upper lacquer layer is printed.

Preferably, the protective layer has at least one gap.

Preferably, a security element is inserted into the gap.

Preferably, the protective layer is applied to the entire surface of the substrate.

Preferably, the flat substrate has a soil-repellent protective layer on its two main sides.

The invention also relates to the use of the security paper as defined above for the production of a value document such as a banknote, passport, identification document and the like.

PL 212 423 B1

The invention also relates to a method for the production of security paper intended in particular for the production of a security document such as a banknote, passport, identification document or the like, characterized in that it comprises the following steps:

a) providing a flat substrate i

b) applying a protective layer against dirt, whereby the protective layer is applied by b1) applying a layer of physically drying varnish to the substrate, constituting the lower layer of the protective layer, in contact with the underlying substrate and closing its pores, where this layer it is based on a water-diluted dispersion of aliphatic polyester polyurethanes or styrene-acrylic polyurethanes; and b2) applying an upper layer of varnish, protecting the substrate against the influence of physical and chemical factors, which is formed by one of the following layers:

i. UV-crosslinkable lacquer layer;

ii. a layer of physically drying varnish based on a water dispersion based on styrene-acrylic without a polyurethane component;

iii. a hybrid varnish layer containing both physically drying components and a radiation curable varnish component, based on an aqueous dispersion based on aliphatic urethane acrylates and acrylates with photoinitiators.

Preferably, the upper lacquer layer is additionally cross-linked, cured and / or dried by irradiation with electromagnetic radiation.

Preferably, the provided flat substrate is in the form of unprinted or printed cotton paper.

Preferably, the lower lacquer layer is in the form of a flexible lacquer layer.

Preferably, the lower lacquer layer is applied as a coating with such a density that a smooth and consistent surface is obtained.

₂

Preferably, the lower lacquer layer is applied in a coating weight of from 2.5 to 15 g / m ^2, preferably from 5 to 10 g / m ^2, to the wet weight.

Preferably, the lower lacquer layer is dried prior to the application of the upper lacquer layer.

Preferably, the composition of the upper lacquer layer is selected in terms of its brittleness and surface tension, whereby it is possible to obtain predetermined tactile properties of the security paper, in particular predetermined smoothness, emitted sound and / or stiffness during bending.

Preferably, an image is printed on the substrate prior to the application of the protective layer.

Preferably, the printed image is applied to the lower varnish layer after the lower varnish layer has been applied to the substrate and / or the printed image is applied to the upper varnish layer after the upper varnish layer has been applied.

Preferably, the unvarnished or varnished substrate is printed with a gravure printing technique.

Preferably, the bottom and / or top lacquer layer is applied by flexographic printing.

Preferably, the flexographic printing varnish layers are applied in the form of a coating with a total weight of 3 to 12 g / m ² .

In another preferred variant of the invention, the lower and / or upper lacquer layer is applied by screen printing.

Preferably, the screen-printed varnish layers are applied in the form of a coating with a total weight of 5 to 15 g / m ² .

In another preferred embodiment of the invention, the lower and / or upper lacquer layer is applied by offset printing or by indirect letterpress printing.

Preferably, the protective layer is applied to the entire surface of the substrate.

Preferably, the flat substrate has a soil-repellent protective layer on its two main sides.

Preferably, the flat substrate provided in step a) is in the form of a security sheet having multiple single copies for which steps b), b1) and b2) are each performed at the same time.

Preferably, the lower and upper lacquer layers are applied to the substrate in a row, in a single pass of the lacquer application device.

The protective layer according to the invention comprises at least two lacquer layers, the first, lower lacquer layer being formed as a physically applied layer on the substrate.

With the drying varnish, which contacts the underlying substrate and closes its pores, the second top coat of varnish protects the substrate against physical and chemical influences, as well as provides good protection against liquid and ink penetration.

The invention is based on the finding that the advantageous properties of radiation curable varnishes can also be used in security papers if the recesses, uneven areas and pores of the substrate are first closed by a layer of physically drying varnish. Radiation-cured varnishes, and in particular UV-dried varnishes (hereinafter referred to as "UV varnishes), have the disadvantage that residual monomers and free photoinitiators generally remain in the cavities and pores of the substrate in the form of highly chemically active components after radiation curing, it depends on the quality of the substrate, the intensity of the radiation, the initiating system and the monomer system (UV: ultraviolet radiation).

This problem becomes even more serious if the UV varnish penetrates into the interior of the paper fiber system, which forms e.g. security paper. The complete polymerization of the UV varnish is then no longer possible. It has now been found that the positive properties of varnishing with UV varnishes can be fully exploited with respect to security papers, if combined coatings are used that include at least two varnish layers, where the lower varnish layer contacts the substrate and closes the pores, and the applied top varnish layer is a layer that protects the substrate against the influence of physical and chemical factors.

The flat backing of the security paper is in particular in the form of unprinted or printed cotton paper. Cotton paper from which security and value documents such as banknotes are produced has a high porosity and has surface irregularities including microscopic holes and recesses in which, if the lower lacquer layer according to the invention is not used, residual monomers and photoinitiators from a radiation-curable lacquer layer.

The lower lacquer layer is preferably in the form of a water-dilutable dispersion lacquer layer. Preferably, it is applied to the substrate in the form of a layer with a thickness selected so that a smooth and continuous layer is formed on the substrate. The lower lacquer layer is preferably elastic, which avoids the formation of cracks in the lacquer layer due to mechanical displacement or swelling of the fibers, for example due to their absorption of moisture. This solution has the advantage that the tactile sensations typical of the banknotes, i.e. the stiffness during bending, as well as the characteristic squeezing sound, are retained longer. This has positive effects, especially when the banknote is exposed to extreme climatic conditions and mechanical stresses. Flexible varnishes preferably include polyurethane systems that impart flexibility to the varnishes. These are in particular water-diluted dispersions of aliphatic polyester polyurethanes or styrene-acrylic polyurethanes. The required amount of coating material depends, of course, on the varnish used, the base material used, the degree of roughness, the pore size and the porosity coefficient, among other things.

The top lacquer layer is preferably in the form of a radiation-curable and / or physically drying lacquer layer, which particularly preferably comprises silicones and / or waxes for increasing the anti-contamination effect. The radiation curable lacquer layer is in particular in the form of a ultraviolet (UV) crosslinking lacquer layer (hereinafter referred to as "UV lacquer"). Its extremely high physical and chemical resistance enables a corresponding increase in quality and adaptation to the requirements profile. High physical strength causes, in particular, high abrasion resistance and extends the service life of the security paper.

The greater chemical resistance also makes the protective layer a long-term stable, effective barrier against water vapor and liquids such as printing ink.

The use of UV varnishes also offers many possibilities for selectively influencing the tactile sensation provided by security paper, in particular a banknote. Varying parameters such as brittleness, gloss and smoothness of the overhead protective layer make it possible to directly influence the tactile sensation of coated paper in various ways, in particular its bending stiffness, smoothness and sound. The composition of the UV varnish is preferably selected in particular with regard to its brittleness and surface tension, thanks to which it is possible to obtain predetermined tactile properties of the paper.

Security, in particular a predetermined smoothness, bending stiffness and / or emitted sound.

In addition to radical cross-linking UV varnishes, it is also possible to use cationically cross-linking varnish systems in the radiation-curable varnish layer.

The physically drying lacquer layer constituting the top lacquer layer alternatively comprises water-dilutable dispersions which preferably do not contain a polyurethane component, e.g. based on styrene-acrylic.

It is also possible for the top lacquer layer to include a hybrid lacquer containing both physically drying components such as a water-dilutable dispersion lacquer and a radiation-curable lacquer. When the hybrid varnish dries, water is first physically removed, e.g. by heat, and then the varnish is cured with radiation, e.g. using ultraviolet (UV) radiation. Suitable hybrid varnishes are, for example, aqueous dispersions based on aliphatic urethane acrylates and corresponding monomers or chemically active oligomers, in particular acrylates and photoinitiators.

In a preferred embodiment of the invention, the upper lacquer layer is applied directly to the lower lacquer layer. Alternatively, a further varnish layer containing a water-dilutable dispersion varnish can be placed between the upper and lower varnish layers.

The lacquer layers constituting the protective layer preferably have matching adhesive characteristics, whereby a high-strength bond is created between them. Particularly when the top lacquer layer is applied directly to the bottom lacquer layer, the composition of the bottom lacquer layer is selected in such a way that optimum adhesion of the radiation-cured lacquer applied subsequently to it is ensured. In a preferred embodiment of the invention, optimization of the wettability of the lower lacquer layer is carried out by lowering the glass transition temperature of the lacquer system. This results in both stronger adhesion and a strengthening of the adhesion.

In further preferred embodiments of the invention, the top lacquer layer or the bottom lacquer layer is transparent and colorless. In particular, in the event that the printed substrate should remain as clearly visible as possible, the two varnish layers may advantageously be transparent and colorless. The protective effect is fully maintained and it is possible to choose additional impressions provided by the security paper. However, it is also possible to color at least one of the varnish layers. This allows the valuable document to be advantageously given a slight tint without having to use different materials from which the substrate may be made.

In another preferred embodiment of the invention, at least the top lacquer layer is impregnated against bacteria and fungi.

It was further found that the lower lacquer layer preferably is placed on the substrate at a coating weight of from 1 to 6 g / m ^2, preferably from 2 to 4 g / m ^2. This corresponds to a preferred amount of about 5 to about 10 g / m ² in a non-dried, moist state (e.g. an aqueous lacquer dispersion with a solids content of 40%). In any case, the thickness of the layer must be sufficient to close irregular recesses and pores in the flat substrate. As for the upper layer paint, it is sufficient that it was placed on the substrate as a coating having a lesser density of from 0.5 to 3 g / m ^2, more preferably 1 to 2 g / m ^2. This corresponds to a preferred amount of uncrosslinked lacquer in the range of about 1 to about 2 g / m ² , since the UV systems are so-called "100% systems" (solids content is 100%). In the case of already smoothed and / or compressed in a previous gravure printing process, these values are at the lower extremities of the range, and for raw paper or the back side of sheets printed by a gravure printing process, they are at the upper ends of the range.

In a preferred development of the invention, letters or patterns are printed on the substrate, and then a protective layer is applied to the printed substrate. This also makes it possible to secure the print. The protective layer may also have gaps, for example in the shape of letters or patterns, into which optically variable security elements are introduced or will be introduced later.

In a further preferred embodiment of the invention, the protective layer is applied over the entire surface of the substrate. In the case of, for example, a banknote, it may be advantageous

The flat security paper backing has a soil release liner on two major sides.

The invention further comprises a value document such as a banknote, coupon, certificate, passport, identification document or the like, which includes security paper of the type described above.

In the manufacture of a security paper of the type described above, a flat substrate is provided in step a), and in step b) a protective layer is applied to the substrate to resist dirt. The protective layer is applied by first applying a layer of physically drying varnish to the substrate in step b1), which forms the lower layer of the protective layer, which contacts the underlying substrate and closes its pores, and then in step b2) a layer of varnish is applied to protect the substrate against the influence of physical and chemical factors and constitutes the upper layer of the protective layer.

If it is not possible to apply two layers of varnish using the "wet on wet" method, the lower layer of varnish is dried before applying the top layer of varnish. Drying may be carried out simply by leaving the varnish for a sufficiently long period of time, for example while transporting the sheet over a sufficiently long distance. In order to be able to carry out the lacquering process quickly, it is advantageous from a technological and economic point of view to accelerate the drying with additional measures. For this purpose, dryers are preferably used which include a hot air blower or an infrared radiation source.

The invention has particularly great advantages when the flat substrate is in the form of printed or unprinted cotton paper.

In a preferred embodiment of the invention, the printed image is applied to the substrate prior to the application of the protective layer. Alternatively or additionally, the printed image may be applied to the lower lacquer layer after the lower lacquer layer has been applied to the substrate. Then, the top layer of varnish is applied to the lower layer of varnish and the printed image, which usually does not take up the entire available surface. Of course, it is also possible to consider printing the top lacquer layer as well.

The lower, upper or both lacquer layers are preferably applied using a flexographic printing process. The lacquer layers are preferably applied in the form of a coating with a weight of from 1 to 8 g / m ² . In another preferred embodiment of the invention, the lower, upper or both lacquer layers are applied by screen printing. In this case, the lacquer layers are preferably applied as coatings weighing from 5 to 15 g / m ² . In yet another embodiment of the invention, the bottom and / or top lacquer layer is applied by an offset printing process, a letterpress printing process or an indirect letterpress process.

In a particularly preferred embodiment of the invention, the flat substrate provided in step a) is a security sheet with multiple single copies for which steps b), b1) and b2) are performed at the same time. The lower and upper lacquer layers are particularly preferably applied to the substrate in a row, i.e. in a single pass of the lacquer application device.

The device enabling the above-described method preferably comprises a first lacquer module that applies a lower layer of physically drying lacquer to the substrate, an intermediate dryer that allows the bottom lacquer layer to be dried, a second lacquer module that is applied to the top lacquer layer, and a final dryer that allows drying. and / or hardening of the top lacquer layer.

In order to obtain a constant varnish thickness, the first and / or the second varnish module is in the form of a flexographic printing device comprising a chamber doctor blade, an anilox roller and a plate cylinder. The anilox roller preferably has small cells, the volume / density of which determines the speed at which the varnish is applied. The chamber scraper bar is placed opposite the anilox roller, thanks to which it fills the cells while scraping off the excess varnish. The anilox roller transfers the varnish to the plate cylinder, which is preferably in the form of a rubber cushion. The rubber cushion eventually transfers the varnish to a flat substrate, in particular a sheet of paper or a web of paper.

Furthermore, a lacquer conditioning device is preferably used which allows the lacquer viscosity and the concentration of the cross-linking agent to be adjusted. In the case of varnishes containing radiation curable components, the varnish conditioning device preferably comprises a varnish tempering device that allows the viscosity and flow of the varnish to be adjusted. Because in this way, there are two variables that affect the speed of application of the varnish, namely

Due to the volume of cells and the viscosity of the lacquer, such a flexographic printing device having a chamber doctor blade allows the described lacquering method to be applied, whereby a uniform, homogeneous and coherent lacquer film can be applied to the entire surface of the sheet in a repeatable manner over a very long period of time.

The intermediate dryer is preferably in the form of an adjustable dryer in which the action of infrared radiation and hot air are combined. It is also advantageous to use two drying modules in the intermediate dryer, whereby sufficient drying is guaranteed even with high processing speeds. The post-dryer is preferably in the form of ultraviolet radiation drying modules which are adapted to the wavelength required to cure the upper lacquer layer as well as to the thickness of the layer.

P r z k ł a d 1

The lower layer of elastic varnish was applied by flexographic printing to cotton paper in a varnish application device using a 20 cm ³ / m ² application roller at an application speed of about 2.0 g / m ^{2 of} dry substance. The flexible varnish was in the form of a water dispersion based on styrene-acrylic polyurethane (Proll company code: L51073).

An upper, second layer of elastic varnish was applied to the first varnish layer in a varnish applicator using a 9 cm ³ / m ² application roller at an application rate of about 1.8 g / m ² dry substance. The second varnish was in the form of a UV varnish (Proll company designation: UV L50733 + UV L50734, mixed together in a ratio of 3: 2).

P r z k ł a d 2

The two-layer film was made as described in Example 1. In an apparatus for applying the lacquer used applicator roll 9 cm ³ / m ² and the speed of overlap of about 2.0 g / m ² of dry substance. The second varnish was in the form of a hybrid varnish (Proll company designation: L50807 (matte varnish) + L50806 (glossy varnish), mixed with each other in the ratio 1: 1; both mentioned varnishes contain both physically drying and radiation-curing components and are water dispersions on based on aliphatic urethane acrylates and acrylates with photoinitiators; the matting component is silicon dioxide and is present in both of the above-mentioned varnishes in different amounts).

P r z k ł a d 3

The lower layer of flexible varnish was applied by flexographic printing to cotton paper in a varnish applicator using a 13 cm ³ / m ² application roller at an application rate of about 1.3 g / m ^{2 of} dry substance. The flexible varnish was in the form of a water dispersion based on styrene-acrylic polyurethane (Proll company code: L51073). The upper, second layer of flexible coating is applied to the first lacquer layer in a device for applying the lacquer application roller using 13 cm ³ / m ² at a speed of overlap of about 1.3 g / m ² of dry substance. The second varnish was in the form of an aqueous dispersion based on styrene-acrylic.

Further embodiments of the invention as well as its advantages will be illustrated below with reference to the drawing. For the sake of clarity, the drawing figures do not show the true scale or proportion between the elements.

Fig. 1 shows a detailed cross-section of a banknote having a two-layer protective layer according to an embodiment of the invention, Fig. 2 schematically shows the layer structure of the banknote shown in Fig. 1, Figs. embodiments of the invention, and Fig. 5 schematically shows a sheet varnishing apparatus for carrying out the process according to the invention.

Figures 1 and 2 show a cross-section through the structure of a banknote 10 having a protective double layer 14 according to an embodiment of the invention. The protective layer 14 applied to the cotton paper fiber substrate 12 consists of a lower lacquer layer 16 made of a water-dilutable dispersion lacquer and an upper lacquer layer 18 made of a UV curable lacquer applied thereto.

The lower lacquer layer 16 contacts the paper fiber substrate 12, thereby closing the capillaries in the paper. The varnish layer is applied in the form of a coating of this kind

To obtain a smooth and consistent surface ensuring optimal adhesion of the subsequent UV varnish layer.

The composition of the UV varnish of the upper varnish layer 18 is selected such that the desired tactile properties of the note and its soil resistance are obtained. In particular, the brittleness of the UV varnish is selected such that the desired tactile properties of the note and the sound produced by the note are obtained. The contamination resistance of the banknote depends essentially on the selected surface tension of the UV lacquer. The high resistance to physical and chemical factors of the UV varnish gives the banknote 10 high abrasion resistance and excellent resistance to water vapor and liquid penetration. The multitude of the UV varnish parameters that can be selected also allows new properties related to the tactile properties of the banknotes and the sound emitted by the banknotes to be obtained compared to the possibilities so far available in the field of security printing.

In the embodiment shown in FIG. 1 and FIG. 2 is diluted with water lacquer dispersion of the lower layer 16 of lacquer is applied to the substrate 12 constituting the cotton paper at a coating weight of 3 g / m ^2, and the UV coating of the upper layer coating 18 in the form of a coating of weight 1.5 g / m ² . In this embodiment of the invention, the water-dilutable varnish of the lower layer of protective lacquer 16 is in the form of a styrene-acrylic polymer and the UV lacquer of the top lacquer layer 18 is in the form of an acrylate system.

Although Figures 1 and 2 show a protective layer 14 arranged on unprinted paper, the substrate 12 may of course be printed. This is schematically illustrated in Fig. 3. On the cotton paper substrate 12 of which the banknote 10 is made, an image 20 comprising letters or patterns is printed, and a protective layer 14 is applied to the printed image 20 and the substrate 12. Alternatively or additionally between the lower one. the printed image 22 may be provided with the lacquer layer 16 and the UV lacquer top layer 18, as shown in Fig. 4.

FIG. 5 shows a sheet varnishing apparatus 30 for applying a coating according to the invention consisting of two varnish layers. The sheet varnishing apparatus 30 includes a varnish conditioning apparatus (not shown here), two varnish modules 32 and 36, an intermediate dryer 34, and an after dryer 38.

The varnish conditioning device allows the varnish viscosity and the concentration of the cross-linking agent to be adjusted. The temperature control device allows the viscosity and flow of the UV varnish to be adjusted.

The first and second varnish modules 32, 36 are modern flexographic printing devices, each comprising a chamber doctor blade, an anilox roller and a plate cylinder. The anilox roller has small cells, the volume of which determines the speed of applying the varnish. The chamber scraper bar is placed opposite the anilox roller, thanks to which it fills the cells while scraping off the excess varnish. The anilox roller transfers the varnish to the plate cylinder, which is in the form of a rubber cushion. The rubber cushion eventually transfers the varnish to the sheets of security to be coated.

The protective layer can also be applied to the endless web. This is especially advantageous for unprinted paper webs.

The intermediate dryer 34 in the form of a dryer in which infrared radiation and hot air are combined comprises two drying modules, whereby, even with high processing speeds, sufficient drying is guaranteed. In the final dryer 38 the UV lacquer layer is cured by irradiation with high intensity ultraviolet light, the protective layer being additionally dried using infrared radiation and hot air. The intensity and wavelength used in the drying modules of the final dryer 38 are adapted to the wavelength required to cure the UV lacquer as well as to the thickness of the layer on the security sheet.

Claims (41)

Security paper for the production of valuable documents such as bank notes, passports, identification documents and the like, comprising a flat backing (12) which at least partially has a dirt-repellent protective layer (14), extending the durability and suitability of the document for use in circuit, characterized in that the protective layer (14) comprises at least two lacquer layers (16, 18), the first lower layer PL 212 423 B1 of the varnish (16) is formed in the form of a layer of physically drying varnish applied to the substrate (12), in contact with the underlying substrate (12) and closing its pores, where this layer is based on a dispersion diluted with water aliphatic polyester polyurethanes or styrene-acrylic polyurethanes, and the second upper lacquer layer (18) is a layer that protects the substrate (12) against the influence of physical and chemical factors and is made of one of the following layers: a) UV-crosslinkable lacquer layer; b) a layer of physically drying varnish based on an aqueous dispersion based on styrene-acrylic without a polyurethane component; c) a hybrid varnish layer containing both physically drying components and a radiation curable varnish component, based on an aqueous dispersion based on aliphatic urethane acrylates and acrylates with photoinitiators. 2. The security paper according to claim 1 The method of claim 1, wherein the substrate (12) is in the form of unprinted or printed cotton paper. 3. The security paper according to any of claims 1 to 3. A method as claimed in any of claims 1 to 2, characterized in that the lower lacquer layer (15) forms a smooth and contiguous layer on the substrate. 4. Security paper according to any one of claims A method as claimed in any one of claims 1 to 3, characterized in that the first, lower lacquer layer (16) is flexible. 5. Security paper according to any one of claims 1 to 5. A method according to any of the claims 1 to 4, characterized in that the second upper lacquer layer (18) comprises silicones and / or wax. 6. Security paper according to any one of claims according to any of the claims 1 to 5, characterized in that the layer of lacquer crosslinkable under the influence of ultraviolet UV radiation is based on an acrylate system. 7. The security paper according to claim 1 according to any of the claims characterized in that the composition of the upper lacquer layer (18) is selected in terms of its brittleness and surface tension. 8. Security paper according to any one of claims A method according to any of the claims 1 to 7, characterized in that the upper lacquer layer (18) is placed directly on the lower lacquer layer (16). 9. Security paper according to any one of claims 1 to 9. A method according to any of the claims 1 to 8, characterized in that between the upper lacquer layer (18) and the lower lacquer layer (16), a further lacquer layer made with the use of a water-dilutable dispersion lacquer is placed. 10. Security paper according to any one of claims 1 to 10. A method according to any of the claims 1 to 9, characterized in that the lacquer layers (16, 18) constituting the protective layer (14) have matching adhesive characteristics. 11. Security paper according to any one of claims A method as claimed in any of the claims 1 to 10, characterized in that the lower lacquer layer (16) has a low glass transition temperature. 12. Security paper according to any one of claims 1 to 12. A method as claimed in any of claims 1 to 11, characterized in that the upper lacquer layer (18) and / or the lower lacquer layer (16) are transparent and colorless. 13. Security paper according to any one of claims A method according to any of the claims 1 to 12, characterized in that the upper lacquer layer (18) is protected against the action of bacteria and fungi. 14. The security paper according to any one of claims 1 to 13, characterized in that the lower lacquer layer (16) is arranged on the substrate (12) in the form of a coating weight of from 1 to 6 g / m ^2, preferably from 2 to 4 g / m ^2. 15. Security paper according to any one of claims 1 to 5. from 1 to 14, characterized in that the top lacquer layer (18) is arranged on the substrate (12) in the form of a coating having a weight of from 0.5 to 3 g / m ^2, more preferably 1 to 2 g / m ^2. 16. The security paper according to any one of claims from 1 to 15, characterized in that the substrate (12) is printed with letters or patterns, and the protective layer (14) is applied to the printed substrate (12) and / or the lower lacquer layer (16) is printed onto which the upper the lacquer layer (18) and / or the top lacquer layer (18) is printed. 17. Security paper according to any one of claims characterized in that the protective layer (14) has at least one gap. 18. The security paper according to claim 1 17. The method of claim 17, characterized in that a security element is inserted into the gap. 19. Security paper according to any one of claims A method as claimed in any of the claims 1 to 18, characterized in that the protective layer (14) is applied to the entire surface of the substrate (12). PL 212 423 B1 20. Security paper according to any one of claims A method as claimed in any of the claims 1 to 19, characterized in that the flat substrate (12) has a dirt-repellent protective layer (14) on its two main sides. 21. Use of a security paper as defined in claim 1; 1 to 20 for producing a value document such as a banknote, passport, identification document and the like. 22. A method of producing security paper intended in particular for the production of a security document such as a banknote, passport, identification document or the like, characterized in that it comprises the following steps: a) providing a flat substrate (12); and b) applying a protective layer (14) to the substrate (12), whereby the protective layer (14) is applied by b ₁ ) applying to the substrate (12) a layer of physically drying varnish constituting the lower varnish layer (16) of the layer (14) ) a protective layer in contact with the underlying substrate (12) and closing its pores, wherein the layer is based on a water-diluted dispersion of aliphatic polyester polyurethanes or styrene-acrylic polyurethanes; and b ₂ ) applying the upper layer of varnish (18), protecting the substrate (12) against the influence of physical and chemical factors, which is formed by one of the following layers: i. UV-crosslinkable lacquer layer; ii. a layer of physically drying varnish based on a water dispersion based on styrene-acrylic without a polyurethane component; iii. a hybrid varnish layer containing both physically drying components and a radiation curable varnish component, based on an aqueous dispersion based on aliphatic urethane acrylates and acrylates with photoinitiators. 23. The method according to p. 22, characterized in that additionally c) the top lacquer layer (18) is cross-linked, cured and / or dried by irradiation with electromagnetic radiation. 24. A method according to any one of claims 1 to 24. 22 or 23, characterized in that the provided flat substrate (12) is in the form of unprinted or printed cotton paper. 25. A method according to any one of claims 1 to 25 22 to 24, characterized in that the lower lacquer layer (16) is in the form of an elastic lacquer layer. 26. A method according to any one of claims 1 to 26. 22 to 25, characterized in that the lower lacquer layer (16) is applied in the form of a coating with such a density that a smooth and coherent surface is obtained. 27. A method according to any one of claims 1 to 27. 22 to 26, characterized in that the lower lacquer layer (16) is applied as a coating weight of from 2.5 to 15 g / m ^2, preferably from 5 to 10 g / m ^2, to the wet weight. 28. The method according to any one of claims 1 to 28 22 to 27, characterized in that the lower lacquer layer (16) is dried before the application of the upper lacquer layer (18). 29. A method according to any one of claims 29 to 29. 22 to 28, characterized in that the composition of the upper lacquer layer (18) is selected in terms of its brittleness and surface tension, so that predetermined tactile properties of the security paper, in particular predetermined smoothness, sound and / or or stiffness during bending. 30. The method of any one of claims 30 to 30 22 to 29, characterized in that an image (20) is printed on the substrate (12) prior to the application of the protective layer (14). 31. A method according to any one of claims 1 to 31 22 to 30, characterized in that the printed image (22) is applied to the lower varnish layer (16) after the lower varnish layer (16) is applied to the substrate (12) and / or the printed image is applied to the upper varnish layer (18) after applying the top coat of varnish (18). 32. A method according to any one of claims 1 to 32. 22 to 31, characterized in that the unvarnished or varnished substrate (12) is printed with a gravure printing technique. 33. The method according to any one of claims 33 to 33. 22-32, characterized in that the lower and / or upper lacquer layer (16, 18) is applied by flexographic printing. 34. The method according to p. 33. The method according to claim 33, characterized in that the lacquer layers applied by flexographic printing are applied in the form of a coating with a total weight of 3 to 12 g / m ² . 35. A method according to any one of claims 1 to 35 22 to 32, characterized in that the lower and / or upper lacquer layer (16, 18) is applied by screen printing. PL 212 423 B1 36. The method according to p. The method of claim 35, characterized in that the varnish layers applied by screen printing are applied in the form of a coating with a total weight of 5 to 15 g / m ² . 37. A method according to any one of claims 1 to 37. 22 to 32, characterized in that the lower and / or upper lacquer layer (16, 18) is applied by offset printing or by indirect letterpress printing. 38. The method according to any one of claims 1 to 38. 22 to 37, characterized in that the protective layer (14) is applied over the entire surface of the substrate (12). 39. The method of any of claims 1 to 39 22 to 38, characterized in that the flat substrate (12) has a dirt-repellent protective layer (14) on its two main sides. 40. The method of any of claims 1 to 40 22-39, characterized in that the flat substrate (12) provided in step a) is in the form of a security sheet having multiple single copies for which steps b), b1) and b2) are each performed at the same time. 41. The method according to any one of claims 41 to 22 to 40, characterized in that the lower and upper lacquer layers (16, 18) are applied to the substrate in a row in a single pass of the lacquer application device.